Irradiated polymers



Y 3',082, l Patented Mar. 19, 1963 3,082,161 IRRADIATED POLYMERS Gaetano F. DAlelio, 2011 E. Cedar St., South Bend, Ind. No Drawing. Filed Jan. 6, 1958, Ser. No. 707,084 17 Claims. (Cl. 204-154) This invention relates to improvements in linear, aliphatic, saturated polymeric esters. More specifically, it relates to the irradiation of such compositions, sometimes hereinafter referred to as polymers or polymeric materials, in the presence of polyunsaturated modifiers, as defined hereinafter and sometimes herein referred to as modifier, and improved products obtained thereby.

In the past there have been certain limitations in the properties of saturated polymeric ester resins. .In order to have solubility and low melting characteristics desirable for application of such resins for many purposes, such as coatings or shaped articles, it has been necessary to sacrifice somewhat the solvent resistance and high melting point or heat resistance desired in finished articles made from these resins. Attempts have been made to efiect improvements in such desired properties by incorporating in the resins substituents having unsaturation of a nature which might cause crosslinkages by posttreatment after application or shaping of the resin. However, dilficulty in controlling the amount and the timing ofsuch crosslinking and increased tendency of such materials to discolor have left much to be desired in that practice.

In accordance with the present invention, it has been found, however, that linear, aliphatic, saturated polymeric esters can be irradiated in intimate contact with polyunsaturated modifiers, as defined hereinafter, to give products having improved properties, such as greater solvent and heat resistance and better strength characteristics than the original polymer had. Furthermore, these irradiated products can be hydrolyzed or saponified to give materials or monomeric units difierent from those of which the polyester resins were originally constituted.

The polyunsaturated modifiers used in the practice of this invention have the formula:

A-Z-A wherein A is selected from radicals of classes I, II and III, of the formulas indicated below and A is selected from the same classes but from a class other than that from which A is selected:

0-(3C=CHR" II. o Ill .lO(CR"' -nC=CH1 III. 1 1

-0-(0R"',)o ,,-c=om in which formulas R is hydrogen, chlorine or a methyl group; R" is hydrogen or a methyl group; R'" is hydrogen or an alkyl group which can have substituted thereon hydrocarbon, hydroxy, alkoxy, aryloxy, aralkoxy, alkaryloxy, and acyloxy radicals; n is a whole number; and Z is a divalent radical with at least two carbon atoms between said valencies and is selected from the class consisting of alkylene, arylene, and alkylene-arylene groups which can have substituted thereon hydrocarbon, hydroxy, alkoxy, aryloxy, alkaryloxy, aralkoxy, acyloxy radicals, as well as additional groups of the above classes I, II and 111.

While (CR"' in the above formula is a repeating unit, it is actually intended that R' can be different in each case so that the carbon is the repeating part of the unit and each time R can be hydrogen or one of various alkyl groups. For example, in the same compound in one (CR"' group, the R' can be hydrogen in both cases, so as to give CH,; in another group one R'" can be H, and the other can be CH so as to give the radical another (CR"' can have both R'" s as methyl groups so as to give the radical in another group one R' can be hydrogen and the other ethyl so that the radical will be CgH; in another group one R' can be an octyl group and the other R' be a nonyl group so that the radical in that case will be 7 I lllHio JMHU etc. The overall (C group as well as any aliphatic portion of Z can contain unsaturation. The length of an aliphatic group in the polyunsaturated -ester can be unlimited, regardless of whether the length of the aliphatic chain results from having n be a large number, or by havingR' in either or both cases be a long aliphatic chain, or by having Z consist of a long aliphatic chain. Moreover, the radical on one side of the central portion Z can differ from the radical on the other side of the central portion Z even though most of the illustrations herein show similar radicals on the two, sides. Such polyunsaturated compounds, hereinafter referred to as polymnsaturated esters, can be derived from polyhydric compounds of the formula HOZOI-I or hydroxy acids of the formula HO-ZCOOH, with Z as defined above. Depending upon the particular polyunsaturated ester selected, the ester can be derived by reaction of the proper polyhydric alcohol or hydroxy acid with the proper acrylic derivative or unsaturated alcohol or derivative. 1

Examples of various polyhydric compounds from which the polyunsaturated esters can be prepared are: ethylene glycol, trimethylene glycol, 2,3-dihydroxy-butane, 1,4-dihydroxybutane, 1,3-dihydroxy-2-phenylbutane, 1,6-dihydroxy-hexane, 1,8-dihydroxy-octane, 2-11-dihydroxy-dodecane, 2,11 -dimethyl-2,1ldihydroxy-dodecane, 2,2-dimethylpropanediol-1,3, 3-methylpentanediol-1,4, 1,1-diethylbutanediol-1,4, 4,5-dihydroxynonane, pentamethylenei glycol, heptamethylene glycol, nonamethylene glycol,. decamethylene glycol, glyceryl monoacetate, glyceryl mon obenzoate, resorcinol, hydroquinone, catechol, dihydroxynaphthalene, trihydroxy benzene, trihydroxy naphthalene, dihydroxymethylnaphthalene, dihydroxy-ethyl naphthalene, dihydroxy-ethoxy-naphthalene, dihydroxy-diphenyl, dihydr'oxy phenethoxy diphenyl, (ethylphenyl) hydroquinone, (ethyl-phenoxy)resorcinol, 2phenoxy-propane- 1,3-diol, beta-ethylolhydroxy-diphenyl, gamma-hydroxypropyl-phenol, Z-hydroxy-8-phenylolnonane, 1,8 lihy.- droxy-4-phenyl-nonane, dihydroxy-toluene, dimethylolbenzene, di-(beta-ethylol)-benzene, di-(alpha-ethyloD- benzene, di-(beta-ethylol)naphthalene, bisphenol or 2,2- di-(p-phenylol) -propane, beta-ethylolphenol, beta-ethylolnaphthol, omega-hydroxy-n-octyl-phenol, n-octyl-resorcinol, alpha-methyl-heptylresorcinol, sec-butyl-resorcinol, ethoxy-resorcinol, 1,8-dihydroxy-4-acetoxy-octane, phenoxy resorcinol, beta-phenylethoxy hydroquinone, (ethylphenoxy)-catechol, acetoxy-dihydroxy-naphthalene, benzoxy-resorcinol, octoxy-bisphenol, 1,4-dihydroxy cyclohexane, 1,3-dihydroxy-Z-cyclohexyl-propane, etc.

Examples'of hydroxy acids, from which various polyunsaturated esters of the above formulas can be prepared, include: hydracrylic acid, beta-hydroxybutyric acid, epsilon hydroxycaproic acid, sabinic acid, juniperic acid, jalapinolic acid, omega-hydroxydecanoic acid, hydroxybenzoic acid, protocatechuic acid, beta-ethylol-benzoic acid, phenylol-acetic acid, phenylol diacetic acid, methylolbenzoic acid, tropic acid, ricinoleic acid, ambrettolic acid, allyl-hydroxy-naphthoic acid, 3,4-dihydroxy-cinnamic acid, hydroxy naphthoic acid, methylol naphthoic acid, acetoxy hydroxy-naphthoic acid, benzoxy-hydroxynaphthoic acid, ethyl-hydroxy-naphthoic acid, octoxyhydroxy-benzoic acid, 5 hydroxy-8-benzoxy-nonoic acid, 5-hydroxy-8-butoxy-nonoic acid, phenylol-benzoic acid, phenylol-ethyl-benzoic acid, etc.

Except for practical limitations of availability, there is no upper limit to the number of carbon atoms between the hydroxy groups or between the hydroxy and carboxylic group since irradiation, particularly when Z is aliphatic, can also cause cross linkage through that part of 'the molecule.

The various acrylic radicals of the above group I are acrylic and its alpha-methyl (methacrylic), alpha-chloro (chloracrylic), beta-methyl (crotonic) alpha-chloro-betamethyl and'alpha-bet-a-dimethyl derivatives.

Examples of unsaturated alcohols which can be used in the preparation of compounds of the above formulas include: vinyl, isopropenyl, alpha-chloro-vinyl, allyl, methallyl, alpha-phenethyl-allyl, beta-chlorallyl, alphaphenyl-allyl alcohols, 2-methylol-butadiene-l,3, 7-hydroxy-octene-l, 7-hydroxy-Z-rncthyl-octene11, 2-hydroxy- 2 methyl-ctadiene-4,7, 3 hydroxy 3 methyl-butene 1, penteh-l-ol-S, 2,5-dimethyl-S-hydroxy-hexene-1, l7- hy'droxy-octadecene-l; 5-acetoxy-7-hydroxy-octene-1, 5- phenoxy-7-hydroxy-octene-l, etc. with polyhydric compounds and hydroxy-carboxylic acids of the formulas HO-Z-OH and HO-ZCOOH, with Z as defined above.

Polyunsaturated esters which can be used in the prac tice of this invention include: the vinyl ether of ethylene glycol monoacrylate; the allyl ether of trimethylene glycol monomethacrylate; the methallyl ether of tetramethylene glycol monochlorac-rylate; the chlorallyl ether of penta- 3 methylene glycol monocrotonate; the mono(beta-methylchloracrylate) of the isopropenyl ether of 1,4-dihydroxy- Z-phenyI-butane; the alpha-phenyl-allyl ether of the monoacrylate of 2,ll-dimethyl-2,ll-dihydroxy-dodecane; the monoacrylate monocrotonate of the glyceryl monoether of 7-hydroxy-octene-l; the isopropenyl-ether of the monoaorylate of 2,11-dihydroxy-dodecene-6; the monoether of 2-methylol-l,4-butadiene and the monomethacrylate of 2,1l-dihydroxy G-vinyl-dodecane; the monoether of 2-hydroxy-2-methyl-octadiene-4,7 and the monoacrylate of 2,34-dihydroxy-2,3,34,35-tetrahydrolycopene; the isopropenyl ether of the monochloracrylate of hexa-t methylene glycol; the mono-(alpha, beta-dimethyl-acrylate) of the 7-hydroxy-octene-1 ether of 1,8-dihydroxyoctane; the morroaorylate of the 3-hydroxy-3-methylbutene-l ether of resorcinol; the monomethacrylate of the ether of pentene-l-ol-S and dihydroxynaphthalene', the monomethacrylate of the ether of 2,5-dimethyl-5 hydroxy-hexene-l and dihydroxy-methyl-diphenyl; the monoacrylate of the ether of 17-hydroxy-octadecene-1 and dihydroxy-acetoxy-naphthalene; the monocrotonate of the ether of 5-acetoxy-7-hydroxy-octene-1 and di- (beta+ethylol)-benzene; the monoacrylate of the ether of 5-phenoxy-7-hydroxy-octene-1 and benzoxy resorcinol; the monoacrylate of the vinyl ether of beta-ethylol phenol; the monomethacrylate of the allyl ether of omega-hyo y-n-octyl-phenol; the monochloracrylate of the methallyl ether of ethoxy' resOrcino'l; the mon y e 0f the isopropenyl ether of phenoxy-hydroquinone; the monoacrylate of the isopropenyl ether of beta phenylethoxyhydroquinone; the monomethacrylate of the isopropenyl ether of 1,8-dihydroxy-A-acetoxy-dodecane; the monoacrylate of the vinyl ether of (ethylphenoxy) -dihydroxynaphthalene; the monoacrylate of the diisopropenyl ether of trihydroxy-naphthalene; the monoacrylate, monochlorac-rylate of the allylethe-r of 2,5,7-trihydroxy-octane, etc.

Such polyunsaturated esters also include: vinyl betaacryloxy-butyrate; methallyl epsilon-methacryloxy-caproate; isopropenyl omega-chloracryloxy-dodecanoate; vinyl beta-acryloxy-propionate; allyl ll-crotonoxy-hexadecanoate; a-phenyl-allyl omega-acryloxy decanoate; (l-methyl- S-vinyl-n-pentyI) p-acryloxy-benzoate; (alpha, alphadimethyl-allyl) (beta-methyl-chloracryloxy)-ethoxy-benzoate; (3-vinyl-n-propyl) p-acryloxyphenyl-acetate; (1,1- dimethyl 3 isopropenyl-propyl-acryloxy-methoxy-benzoate; (1methyl-1S-vinyl-n-pentadecyl) 2-acryloxy-2- phenyl-propionate; (l-methyl-3-acetoxy-5-vinyl-n-pentyl) (alpha, beta-dimethyl-acryloxy) -naphthoate; (1-methyl3- phenoxy-S-vinyl-n-pentyl) (acryloxy-methoxy)-naphthoate; isopropenyl 12-acryloxy-octaden-9-oate; allyl-16- methacryloxy-hexadecen-7-oate; 2-methyl-r0ctadiene-4J- yI-Z-chloracryloxy-(aoetoxy-naphthoate); methallyl 5 methacryloxy-8-benzoxy-nonoate; chlorallyl crotono ryethyl-naphthoate; allyl methacryloxy-octoxy-benzoate; aphenyl-allyl 5 crotonoxy-nonoate; vinyl-bis-(acryloxyphenyD-benzoate; chlorallyl (acryloxy-pherroxy-ethynbenzoate; vinyl 3 acryloxy-Schloracryloxy-palmitate; vinyl beta-vinyloxy propionate; vinyl beta-allyloxy propionate; vinyl beta-methallyloxy-butyroate; allyl epsilonallyloxy-caproate; chlorallyl omega-isopropenyloxy-nhexadecanoate; alpha-phenyl-allyl 11-(1-methy1-5-vinyl- 1 methyl-S-vinyl-peutyl n-p entyloxy) -n-hexadecanoate; omega (l methyl 5 vinyl n pentyloxy) n decanoate; alpha, alpha-dimethyl allyl (alpha-phenyl-all'yloxy)-benzoate; 3-vinyl-n-propyl (3-vinyl-n-propyloxybet-a-ethoxy)-benzoate; vinyl (1,3-dimethyl-3-is0propenyl-n-propoxy-p'henyl) acetate; 1-methyl-15-vinyl-n-pentadecyl alpha-phenyl-rbeta-( l-methyl-3nacetoxy-5-vinyl-pentyloxy) -propionate; isopropenyl (l-methyl-3-phenoxy-5- vinyl-pentyloxy) -naphthoate; (1 methyl-n-heptadecyl) (vinyloxy-methyl)-naphthoate; i-sopropenyl acetoxy-( 1- methyl-S-vinyl-pentyloxy) -naphthoate; (3-vinyl-n-propyl) ethyl-(1,Z-dimethyl-allyloxy)-naphthoate, methallyl octoxy-(ally1oxy)-benzoate; alpha-phenyl-allyl 5-,vinyloxy- 8-benzoxy-n-nonoate; methallyl bis(vinyloxyphenyl)-benzoate; vinyl ethyl-(vinyloxyphenyl)-benzoate; vinyl 3,5- diallyloxy-palmitate; vinyl beta, beta-bis-acryloxy-propionate; divinyl alpha acryloxy-succin-a-te; l-methyl-4,6diallyloxy-heptyl acrylate; 'vinyl bis-(isoproperryloxyphenyl) -benzo'ate; diallyl (beta-allyloxy-ethyl) -terephthalate, etc.

From the results of this invention, it is apparently advantageous to have the unsaturated groups separated from each other to a greater degree than exists in such materials as divinyl ether and allyl methacrylate which latter materials do not give the effective results produced by the present invention. It is preferred that there be at least six carbon atoms separating the unsaturated groups.

Methods for the preparation of the polyunsaturated esters of the type indicated herein are well knownjn the art. Where the desired compound is one which can be represented by the formula I--Z-IH, it can be derived from a polyhydric compound. -It is generally advantageous to prepare the ether portion of the compound first. This can be done by starting with the polyhydric compound or with a. derivative of such compound which will give an intermediate having the desired structure in the Z portion of the molecule. Then the radical of formula III can be added by using an equivalent amount of unsaturated alcohol of the desired structure to substitute on a second hydroxy group of the polyhydric compound. This can be done by well-known procedures for making unsaturated ethers from unsaturated alcohols and polyhydric compounds.

This can also be done by starting with a compound which is the counterpart of the polyhydric material but which has chlorine groups in place of the hydroxy groups in at least the position which is first to be substituted. For example, if the desired compound is a derivative of ethylene glycol, the starting material can be ethylene chlorhydrin so that the ether part of the derivative can be formed by reacting the unsaturated alcohol either as the sodium alcoholate or in the presence of sodium hydroxide so as to prepare the ether derivative. Such procedures are well known. After this intermediate has been recovered, the acrylic group can be added by using the stoichiomet-ric amount of acrylic anhydride to react with the remaining hydroxy group.

Alternately, the corresponding acrylyl chloride compound can be used with the ether intermediate in the presence of an amine which will take up the hydrogen chloride liberated by the reaction. If desired, the starting material can be the counterpart of the polyhydric compound in which the hydroxy groups have all been replaced by chlorine atoms. In such case the ether group is added as before by adding the stoichiometric amount of sodium alcoholate or of alcohol and sodium hydroxide, and then the acrylic radical can be attached by adding the acrylic compound in the formof its sodium salt so that sodium chloride will split out and thereby form the acrylic ester.

When the desired compound is one having the formula IZII, the starting material can be an hydroxy carboxylic acid. In such cases, it is generally advantageous first to react the carboxylic group with the unsaturated alcohol to form the unsaturated ester group. While other suitable methods can be used, it is generally easiest to form the sodium; or other alkali metal salt of the can boxylic acid groups and use the ohloro homolog of the unsaturated alcohol so that the unsaturated ester will be formed upon the splitting off of sodium chloride. The hydroxy group of the hydroxy acid can then be substituted with a radical of Formula I by using the proper acrylic anhydride or acrylyl chloride according to the procedure indicated above for preparing acrylic esters.

When the desired compound has the formula II- ZIII, the starting material again can be an hydroxy carboxylic acid. If the ether and ester portions of the product are to be derived from the same unsaturated alcohol, the product can be prepared in one step by using sufficient alcohol to substitute in both positions and the conditions used would be the standard conditions used for making unsaturated ethers. In some cases, where the unsaturated ether and ester radicals are to be different, the same group can first substituted on the ether and ester portions of the molecule and the proper ester group substituted later by ester interchange using the stoichiometric amount of second ester or alcohol for interchange. Very often, depending on the relative sizes and reactivities of the alcohol groups to be substituted, the carboxylic group can be first esterified with a saturated alkyl group, and ester interchange be performed either before or after the ether formation. Similarly a chloroester or chloro-acid counterpart of the hydroxy-carboxylic acid can often be used. In such cases the proper ester group can be introduced as indicated above and then the ether group introduced by reaction with the sodium alcoholate of the unsaturated alcohol. Generally, however, the ether-ester can be prepared simply by adding the proper amount of unsaturated alcohol to the hydroxy-acid or chloro-acid and then, after the esterification step has been completed, 'proceeding with etherification of the intermediate as indicated above. In any case, the preparations are well the skillof any chemist. Modifications would be obvious when addi- 6 tional groups of types I, II and I11 are desired in the molecule.

Purification of the polyunsaturated esters can be effected in a variety of ways, for example, by distillation in the presence of polymerization inhibitors, by crystallization from solution, extraction, etc.

In view of the great tendency of said polyunsaturated esters to polymerize, it is most surprising to find that these compounds react to orosslink the {polymer molecules instead of forming bomopolymlers themselves which would be 'heterogeneously dispersed in the polymeric material.

Sometimes the strong tendency of aorylates to form homopolymers actually results in cloudiness or small fisheyes being formed in the irradiated resin. In such cases it is preferred to use an inhibitor for addition polymerizations such as t-butyl catechol, di-Hbutyl-p-cresol, or other inhibitors well-known in the art to retard addition polymerization.

As indicated above it is advantageous to have the unsaturated groups of the modifier well spaced from each other. It is also desirable that there be a high proportion of hydrocarbon groups, such as methylene groups, spacing the unsaturated groups. This improves the resistance of the modifier to decomposition, discoloration and odor and taste formation upon irradiation. For example, the use of modifiers made from polyglycols having a high proportion of oxygen therein such as polyalkylene glycols, i.e. hexaethylene glycol, etc. is undesirable. Thus, the use of modifiers described herein is much more satisfactory than the use of the diacrylate of hexaethylene glycol. In the latter case, the high prm portion of oxygen results in decomposition, discoloration, odor and taste upon irradiation. Such changes are objectionable in many of the uses to which the irradiated product is to be put.

It has been found, in accordance with this invention, that comparable or higher degrees of oros'slinking can be effected in the polymers with lower irradiation doses in the presence of the polyunsaturated modifiers than is effected on the polymers not containing such modifiers. Furthermore, polymers irradiated without these modifiers are more brittle and stiffer than polymers irradiated with these modifiers.

The linear, saturated aliphatic polyesters used in the practice of this invention can advantageously be prepared from dihydroxy alkanes, such as ethylene glycol, and dicanboxylic aliphatic acids, such as succinic acid, or from aliphatic compounds containing an hydroxy and carboxylic acid group in the same molecule. While the dihydroxy and dicarboxylic compounds are advantageous in the preparation of linear polyesters, it is possible and very often desirable to use other polyhydric alkanes and other polycarboxylic aliphatic acids in quantities or under conditions which give polymers which are not substantially crosslinked. For example, glycerine can be used in such amounts or under conditions controlled so as to give very little or no orosslinking. Thus suocini'c acid or anhydride can be reacted with less than the stoichiometric amount of ethylene glycol. Then, when the esterification reaction is substantially completed, glycerine can be added in such a calculated amount that only two hydroxy groups of the glycerine can enter the reaction to complete esterification with the free carboxylic acid groups in the reaction mixture. Furthermore, polyhydric and polycarboxylic aliphatic compounds of the type indicated canbe partially esterified so that there are substantially only two hydroxy or carboxylic acid groups available to participate in the polyrnlerization reaction. Thus, the monostearate of glycerine, or the dicaproate of pentaerythritol, or the monohexyl ester of tricanballylic acid can be used.

Methods of preparing the polyesters are well known in the art. The acids and the glycols, or the hydroxy acids, can be used in these preparations, or where desirable or advantageous various derivatives, such as the esters, anhydrides, acid chlorides, etc., can be used. Generally, for high molecular weight polyesters it is necessary or desirable to conduct the esterification under reduced pressures.

-It has been noted that polymers having molecular weights greater than about 6,000 can easily be converted to insoluble products in accordance with the practice of this invention. With polymers of lower molecular weight, it is necessary to expose them to correspondingly greater amounts of irradiation to reach the insoluble stage. However, it is contemplated that irradiation treatment of such lower molecular weight polymers for other purposes as described hereinafter, for example 3,000 and even lower, is within the scope of this invention, even though the irradiation is not carried on far enough to efiect insolubility. For such lower molecular weight polymers a considerable amount of the preliminary irradiation apparently is directed to increasing linear polymer chains, or in changing the type of polymer linkage. After the linear polymer length has reached a certain amount or type, the joining together of polymer chains apparently results in the crosslinking which efiects insolubility. It is also possible that there is a certain amount of decomposition of polymer chains effected by the irradiation resulting in a reduction of molecular weights, which is competitive with the increase of molecular weights caused by tying polymer chains together by irradiation. However, this invention is not considered as restricted to any such theories or explanations, and the scope of the invention is contemplated as herein described and claimed.

It has also been noted that irradiation of the polymers in the presence of the polyunsaturated modifiers as described herein is much more eifective in producing crosslinking of polymer chains, and thereby improvement of properties as above noted, than is the case when the polymers are irradiated in. the absence of these polyunsaturated modifiers. Furthermore, there is less side reaction, such as degradation and discoloration, when these modifiers are used.

For most purposes in the practice of this invention it is generally desirable to have in the polyester molecules a higher proportion of methylene or -CH groups, or of hydrocarbon portion than ester or --COO-- groups. While most of the polyesters shown above are of the more easily available hydroxy and carboxylic acid compounds having a relatively few number of carbon atoms between the esterifiable groups, there is no limitation on the number of carbon atoms which separate the esteri fiable or esterified groups. This is determined by the properties desired in the resultant polyesters, the availability of the materials and the sluggishness of such high molecular weight materials to undergo esterification because of. the higher proportion of non-esterifiable por tions of such materials.

Various hydroxy and carboxylic acid compounds can be used in various combinations of two or more in the preparation of polyesters as indicated herein suitable for the practice of this invention including, but not limited to the following: ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, 2,2-dimethylpropanediol-1,3, 3-methylpentanediol- 1,4, 2,2-diethylbutanediol-1,4, 4,5-dihydroxy-nonane, heptamethylene glycol, nonamethylene glycol, decarnethylene glycol, 3-methylpentanediol-l,5, sebacic acid, azelaic acid, adipic acid, succinic acid, octylsuccinic acid, succinic acids produced by the hydrogenation of condensation products of maleic anhydride with C and similar olefins, malonic acid, methylmalonic acid, methylsuccinic acid, brassilic acid, glutaric acid, pimelic acid, suberic acid, japanic acid, thapsic acid, etc. Hydroxy aliphatic carboxylic acids which can also be used, either alone, in mixtures of two or more with each other, or in mixtures of glycols and polybasic acids to produce esters for the practice of this invention include, but are not restricted to: omega-hydroxy-decanoic acid, beta-hydroxyisobuteric acid, epsilon-hydroxycaproic acid, hydroacrylic acid, sabinic acid, juniperic acid, jalapinolic acid, etc.

The polymers can be in any suitable form for admixing with, or absorbing, or containing the polyunsaturated modifier. For example, it can be in powder, film, fiber, pellet or solution form, so as to present large areas for absorbing or contacting the modifier. Molded articles can also be so treated. If desired, increased temperatures can be used provided the modifier does not thermally polymerize to an undesirable extent at those temperatures.

If the modifier is in liquid or solution form, the admixture can be performed by absorption. For example, the polymers are allowed to stand in the modifier in liquid or solution form until a desired amount has been absorbed or diffused therein. This amount can be determined by periodically removing the polymers, draining or wiping oil the excess liquid and weighing to determine the amount absorbed. Sometimes it may be desirable to allow the so-treated polymers, particularly the more massive structures, to stand for a time sufiicient to permit diffusion of the absorbed material to give more uniform distribution throughout the mass of the polymers.

However, the modifier can be introduced in any other convenient or appropriate manner. For example, the mixture can also be efiected mechanically as on mixing mills, in a Banbury mixer, or in a single or double worm extruder. Since the heat generated in such latter types of mixing may cause polymerization of the modifier, particularly where the latter is very actively polymerizable, this type of mixing is very often best carried out at reduced temperatures, in the presence of an inert atmosphere, such as nitrogen, and/or in the presence of a polymerization inhibitor, such as 2,6-ditertiary-butyl-paracresol, tertiary-butyl-catechol, etc. Such compounded mixtures can then be extruded as fibers, films, rods, etc., or as wire coatings or coatings on fibrous materials for clotheslines, etc., and then irradiated. They can also be extruded in tubular form, such as pipes, molded into shaped articles, or blown into bottles, and in each case then irradiated.

The term irradiation, as used herein, means high energy radiation and/ or the secondary energies resulting from conversion of this electron energy to neutron or gamma radiation, said electron energies being at least about "100,000 electron volts. While various types of irradiation are suitable for this purpose, such as X-ray and .gamma and beta rays, the radiation produced by high power electron linear accelerators has been found to be very conveniently and economically applicable and to give very satisfactory results. However, regardless of the type of irradiation and the type of equipment used for its generation or application, the use thereof in the treatment of polymeric materials as described herein is contemplated as falling within the scope of this invention so long as it is produced by or from electron energy of at least about 100,000 electron volts. While there is no upper limit to the electron energy that can be so applied advantageously, the efifects desired in the practice of this invention can be accomplished without having to go above 50,000,000 electron volts. Generally, the higher the electron energy used, the greater is the depth of penetration into the massive structure of polymeric materials, and the shorter is the time of exposure required to accomplish the desired result. For other type of irradiation, such as gamma and X-rays, energy systems equivalent to the above range of electron volts are desirable.

It is intended that the term irradiation" include what has been referred to in the prior art as ionizing radiation which has been defined as radiation possessing an energy at least sufiicient to produce ions or to break chemical bonds and thus includes also radiations such as ionizing particle radiation as well as radiations of the type termed ionizing electromagnetic radiation.

The term ionizing particle radiation has been used to designate the emission of electrons or highly accelerated nuclear particles such as protons, neutrons, alpha-par ticles, deuterons, beta-particles, or their analogs, directed in such a way that the particle is projected into the mass to be irradiated. Charged particles can be accelerated by the aid of volt-age gradients by such devices as accelerators with resonance chambers, Van de Gratf generators, betatrons, synchrotons, cyclotrons, etc. Neutron radiation can be produced by bombarding a selected light metal such as beryllium with positive particles of high energy. Particle radiations can also be obtained by the use of an atomic pile, radioactive isotopes or other natural or synthetic radioactive materials.

Ionizing electromagnetic irradiation is produced when a metallic target, such as tungsten, is bombarded with electrons of suitable energy. This energy is conferred to the electrons by potential accelerators of over 0.1 million electron volts (mev.). In addition to radiations of this type, commonly called Xqray, an ionizing electromagnetic radiation suitable for the practice of this invention can be ob tained by means of a nuclear reactor (pile) or by the use of natural or synthetic radioactive material, for example cobalt 60.

Various types of high powerelectron linear accelerators are commercially available, for example from Applied Radiation Corporation, Walnut Creek, California. In the following Example I, ARCO type travelling wave accelerator, model Mark I, operating at 3 to million electron volts, was used to supply the irradiation. Other type of accelerators, such as supplied by High Voltage Engineering Corporation, Burlington, Massachusetts, or as described in United States Patent No. 2,763,609 and in British Patent No. 762,953 are satisfactory for the practice of this invention.

In the following examples, the radiation doses are re ported in mega-reps, which represent 1,000,000 reps. A rep is defined, according to Reactor Shielding Design Manual, edited by Theodore Rockwell III and published by D. Van Nostrand Company, Inc., 1st edition, 1956, as that radiation dosage which produces energy absorption in human tissue equal to 93 ergs per gram of tissue.

In the practice of this invention, changes in properties of the polymeric materials can often be noted after treatment with even less than 1 megarep. However, it is generally advantageous to use doses of 2 megareps or more. The degree of change in properties is dependent somewhat on the dosage, greater changes being effected by increasing the dosage.

The polymer material to be treated is often advantageously irradiated while in a container made of a material such as aluminum or glass which will not substantially interfere with the irradiation. It is advantageous also to use polymeric materials, such as polyethylene itself, nylons, i.e. 66 nylon, polycaprolactam, etc. It can also be wrapped in film or foil impervious to vapors and gases, such as aluminum foil, polyethylene film, etc., which will prevent substantially the escape of volatile materials. It is often advantageous to avoid oxidation or side reactions by the use of an inert atmosphere such as nitrogen. Moreover, it is advantageous to prevent the temperature from approaching that at which the polymer material is unstable. This can be accomplished by cooling the polymer material before irradiation, for example with Dry Ice, or by dissipating the heat generated during irradiation.

Various methods of practicing the invention are illus trated by the following examples. These examples are 10 otherwise, refer to parts by weight and percentages by weight. Unless indicated otherwise, the terms polymers and polymeric are intended to include copolymers and copolymeric. Molecular weights given herein are Staudinget molecular weights.

EXAMPLE I ator of the following dosagesz 5, 10, 25, 50 and 100 megareps respectively. In each case the irradiated product is infusible and insoluble in chloroform, and is less stiff and less brittle than the same polyester irradiated in the absence of the polyunsaturated modifier.

Various samples of this same polyester, similarly treated with the polyunsaturated modifier, are exposed to 1X10 roentgens each of gamma radiation, X-rays, neutron radiation from bombarded beryllium, radiation from radioactive cobalt 60, and radiation from a Van de Grafi generator. In each case similar improvements of properties are noted.

EXAMPLE II A polyester prepared from trimethylene glycol and aze- -laic acid, which has a molecular weight of 10,000 and is completely soluble in chloroform, is treated according to the procedure of Example I and similar improvements with respect to stifiness, brittleness, and solvent and heat resistance are noted.

EXAMPLE In A polyester prepared from tetramethylene glycol and adipic acid, which has a molecular weight of 8,000 and is completely soluble in carbon tetrachloride, is mixed on a B-anbury mixer with 8 percent of the allyl ether of octamethylene glycol monoacrylate containing 1 part of di-t- .butyl-p-cresol per parts of acrylate. Upon treatment of various samples with 5 megareps, 25 megareps, and 50 megareps respectively of irradiation as in Example I, the

product is found in each case to be insoluble in carbon tetrachloride, chloroform and methylene dichloride, is infusible, and is improved with respect to stiffness and brittleness over the same polyester irradiated without the polyunsaturated modifier.

EXAMPLE" IV EXAMPLE V A polyester prepared from omega-hydroxy-decanoic acid, having a molecular weight of 6,000 and being completely soluble in chloroform, is mixed in powder form on a mill with 5 percent of the methallyl ether of hisphenol monocrotonate and then extruded into a thin sheet. Samples of this sheet are individually wrapped in aluminum foil and exposed to -15, 25, and 35 megareps of irradiation respectively in accordance with the procedure In each case the irradiated product is insoluble in chloroform, is infusible, and is improved with respect to stifiness and brittleness over the same polyester irradiated without the polyunsaturated modifier.

EXAMPLE v1 Glycols Dibasic Acids K-Sebacic acid. L-Azelaic acid. MBrassi1ic acid. Ncty1succlnic acid. 0-Succinic acid.

A2,2-Dime thylpropanediol-1,3

ntanedio1-l,4 6-4 -Dihy D-l'lecamethylene glycol- E-Tetramethylene glycol..-

F-3-Methylpentancdiol-1,5 P-Pimelicacid. GHexnmethylene glyeol- QAdi ic acid. HEthylene glycol R-Hy ogenated condensation product of Cu olefln and maleic anhydride.

Modifier SVinyl omega-isopropenyloxy-n-hexadecanoate T-Isopropenyl beta-acryloxy-butyrate U-Allyl-5-methacrylox'y-8-benzoxy-nonoate VVinyl .ether of mono-(chloracrylate) of dihydroxy naphthalene W-The ether of 3,S-dimethy1-5-hydroxy-hexene-1 and di-(beta-ethylol)-benzene monoacrylate X-Allyl 3-allyloxy-benzoate Y-Chlorallyl omega-isopropenyloxy-n-hexadecanoate Z-Ally1 p-(pvinylphenyl)-benzoate TABLE Modifier Percent Modifier Polvester Mo]. Wt. Megareps.

In addition to the foregoing modifiers, other materials may be present in minor amounts in the polymeric compositions, added by various well-known means, such as milling, etc. Thus, for example, plasticizers, lubricants, fillers, etc. can be added in accordance with the efiects desired. Suitable fillers are silica, silica aerogel, titanium dioxide, calcium silicate, ferric oxide, chromic oxide, cadmium sulfide, asbestos, glass fibers, calcium carbonate, carbon black, lithopone, talc, etc. Furthermore various modifications and improvements in properties can be effected by admixing these polymeric materials with various other resins regardless of whether such other resins are degraded when irradiated by themselves. Even if so degraded, the crosslinking produced by irradiation with polymeric materials as in this invention results in various novel improvements in the polymeric materials. Such other resins include: polyacrylic esters, polystyrene, polyethylene, chlorinated polyethylene, chlorosulfonated polyethylene, natural and synthetic rubbers, butadiene-acrylonitrile copolymers, neoprenes, polydimethylsiloxanes, styrene-acrylonitrile copolymers, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, polychlorotrifluoroethylene, cellulose, polyisobutylene, etc.

An important feature of this invention resides in the fact that the irradiated product can be hydrolyzed or saponified, according to any of the well-known procedures for saponification, to give various polyfunctional products. For example, compounds having a plurality of functional groups can be prepared. Thus, representing parts of various polymeric molecules used herein, with AZA representing a crosslinking residue of the polyunsaturated modifier, possible products obtained upon hydrolysis or saponification can be illustrated as follows:

A and B represent segments of polyester molecules in which R and R are divalent hydrocarbon groups as indicated above for the linear, aliphatic saturated polyesters. Where the two molecules are crosslinked at the R"" groups, hydrolysis produces a compound having at least two hydroxy groups, with the third functional group depending on the nature of the A or A group attached thereto. Similarly, where the crosslinkage is through the R groups, hydrolysis produces a compound having at least two carboxylic acid groups, with a third functional group depending on the nature of the A or A group attached thereto.

With polymer segments C and D where the crosslinkage is shown between an R and an R" group, the product upon hydrolysis includes derivatives similar to those described above for A and B.

Such compounds can be represented by the following formulas.

Where radical -I is attached to R"":

Where radical I is attached to R:

HOOO-R' coon J) 13 Where radical II or III is attached to R:

HO CR' R" R O 0 H l I Where radical I is attached to R:

HOOCR'- R" R OH (I; l

I H-C|l-COOH H V J Where radical II or III is attached to R:

Accordingly, the saponification product of the irradiated mixture of polymer of omega-hydroxy-decanoic and the methallyl ester of bisphenol-monocrotonate prepared according to Example V includes products fitting one or both of the above formulas, namely monohydroxyundecane-dicarboxylic acid and dihydroxy-undecanemonocarboxylic acid.

Therefore, it can be seen that the foregoing permits the production of various polyfunctional hydroxy and carboxylic acid compounds. This is surprising and especially important in view of the fact that when the corresponding monomeric hydroxy and carboxylic acid compounds are irradiated directly, the monomers generally decompose and do not give the polyfunctional derivatives illustrated above. It is not intended, however, that the invention be restricted to the specific type of products, or linkages, or theories indicated above. It is contemplated that the invention covers whatever products are obtained by the practice taught herein regardless of the exact chemical structure. The foregoing is merely illustrative of the possibilities of the invention.

The hydrolysis can be carried out on any of the irradiated resins produced according to any of the foregoing examples. A suitable procedure is illustrated by the following examples:

EXAMPLE VII Potassium hydroxide is dissolved in alcohol-the amount of KOI-I being slightly in excess of the stoichiometric amount calculated on the basis of the amount of resin to be hydrolyzed. The resin advantageously in powder or flake form and the alcoholic solution are placed in equipment provided with stirrer and reflux condenser. The mixture is stirred and refluxed for about half an hour after the resin has gone into solution. The resultant solution contains the hydroxy derivatives and the potassium salt of the carboxylic acids. The solution is con centrated by distilling off some of the alcohol and the hydroxy and carboxylic acid derivatives separated :by various means such as neutralization, distillation, crystallization, extraction, etc.

14 EXAMPLE vm When the irradiated resins of Examples I-VI inclusive are individually hydrolyzed by the procedure of the preceding example and suificient hydrochloric acid added in each case to react with the potassium present in the product, followed by atmospheric distillation of the volatile materials present and subsequent distillation at reduced pressure, distillates of wide boiling range are obtained in each case. Various fractions of these distillates give tests indicating the presence of hydroxy and carboxylic acid groups.

The compositions produced according to the preceding two examples are particularly useful in the preparation of modified drying oil compositions, wetting agents, detergents, sequestering agents, etc., and are used in the manner in which such products are generally used. As indicated previously herein the irradiated polymeric mate rials produced by the invention disclosed herein, including those containing various modifiers as described, are useful in the production of textile fibers, packaging films, protective coatings and other shaped articles of improved properties such as improved heat and solvent resistance, which fibers, films, etc. are advantageously used for the purposes and in the manner in which such products are generally used.

The amount of polyunsaturated modifier to be added will vary depending on the properties desired in the ultimate product. As would be expected, the greater the amount of such compound used, the greater is the change in properties of the irradiated product. Although even as little as 0.1 percent of polyunsaturated compound often effects notable changes in properties, it is generally advantageous to have at least one percent or more of such modifiers present. There is no upper limit to the proportion of such compound that may be present. However, when there is more than fifty percent present, the properties of the products approach thoseof polymers obtained by irradiation of the modifiers alone. Therefore, to retain characteristics of the' polymeric olefin, it is desirable to have no more than'fifty percent by weight of the modifier. However, in cases where the irradiated product is to be saponified for recovery of the type of products indicated herein, the proportion of modifier is adjusted according to the yield desired for such products, and, especially in cases where the molecular weight of the polyunsaturated modifier is considerably more than the molecular weight of the polymer unit which will be liberated by saponification, then it may be desirable to have greater proportions than fifity percent by weight of the modifier present.

While certain features of this invention have been described in detail with respect to various embodiments thereof, it will, of course, be apparent that other modifications rnay be made within the spirit and scope of this invention and it is not intended to limit the invention to the exact details shown above except insofar as they are defined in the following claims.

The invention claimed is:

l. A process for producing improved polyester resin compositions comprising the treatment of a linear, saturated aliphatic polyester having ester groups in the linear polymer chains thereof, and having at least two carbon atoms between ester groups in the polymer molecule with at least about 2 megareps of high energy, ionizing radiation equivalent to at least 100,000 electron volts while said polyester is in intimate and and substantially uniform mixture with at least 0.1 percent by weight, based on the weight of polyester resin, of a polyunsaturated compound of the formula wherein A is selected from the group of radicals having formulas of classes I, II and III as defined below, and

is also selected from the same group of radicals but from a class other than that from which A is selected:

o(oR"',)...'-( ;=GH= in which formulas, m and m are values selected from the class .consisting of zero and integers, each R is respectively selected from the class consisting of hydrogen, chlorine and the methyl group; R" is respectively selected from the class consisting of hydrogen and the methyl group; each R'" .is respectively selected from the class consisting of hydrogen, alkyl radicals and the hydrocarbon, hydroxy, alkoxy, aryloxy, aralkoxy, alkaryloxy and acyloxy derivatives of alkyl radicals; and Z is a divalent radical having at least two carbon atoms between said valencies and being selected from the class consisting of divalent alkylene, 'arylene, alkylene-arylene radicals and their derivatives having substituents of the class consisting of hydrocarbon, hydroxy, alkoxy, aryloxy, alkaryloxy, aralkoxy, acyloxy and additional radicals thereon selected from said classes I, II and III.

2. A process of claim 1, in which at least 1 percent of said polyunsaturated compound is used.

3. A process of claim 2, in which the irradiated product is subsequently saponified.

4. A process of claim 2, in which said polyunsaturated compound is a monoacrylate of an alkylene glycol.

5. A process of claim 2, in which said polyunsaturated compound is derived from an alkylene glycol having at least six carbon atoms between the hydroxy groups.

6. A process of claim 5, in which said polyunsaturated compound is an alkenyl ether of the monoacrylate of an alkylene glycol having at least six carbon atoms between the hydroxy groups.

7. A process oflaim 2, in which said polyunsaturated compound is an acrylate ester of the alkenyl ester of a hydroxy carboxylic acid having at least six carbon atoms between said hydroxy and carboxylic acid groups.

8. A process of claim 7, in which said hydroxy carboxylic acid is an hydroxy alkanoic acid.

9. A process of claim 2, in which said polyunsaturated A compound is an alkenyloxy derivative of an alkenyl ester of a carboxylic acid.

10. A proces of claim 9, in which said ester has at least six carbon atoms between said alkenyloxy group and the carboxylate group.

11. A process of claim 1 in which said polyester is derived from a dihydroxy alkane and a dicarboxylic alkane.

12. A process of claim 1 in which said polyester is polymeric ethylene glycol sebacate.

13. A process of claim 1 in which said polyester is polymeric tetramethylene glycol adipate.

14. A process of claim 1 in which said polyester is polymeric hexamethylene glycol adipate.

15. A process of claim 1 in which said polyester resin is prepared from an hydroxy alkanoic acid.

16. A process of claim 1 in which said polyester is derived from omega-hydroxy-decanoic acid.

17. A process of claim 1 in which said polyester has a molecular weight of at least 3,000.

Referepces Cited in the file of this patent UNITED STATES PATENTS Canada Jan. 26, 1954 OTHER REFERENCES Ballantine et al.: Brookhaven National Laboratory Report No. 389, pages 6-11, May 1956.

Bovey: Etfects of Ionizing Radiation on Natural and Synthetic High Polymers, pages 173-176. (1958). 

1. A PROCESS FOR PRODUCING IMPORVED POLYESTER RESIN COMPOSITIONS COMPRISING THE TREATMENT OF A LINEAR, SATURATED ALIPHATIC POLYESTER HAVING ESTER GROUPS IN THE LINEAR POLYMER CHAINS THEREOF, AND HAVING AT LEAST TWO CARBON ATOMS BETWEEN ESTER GROUPS IN THE POLYMER MOLECULE WITH AT LEAST ABOUT 2 MEGAREPS OF HIGH ENERGY, IONIZING RADIATION EQUIVALENT TO AT LEAST 100,000 ELECTRON VOLTS WHILE SAID POLYESTER IS IN INTIMATE AND AND SUBSTANTIALLY UNIFORM MIXTURE WITH AT LEAST 0.1 PERCENT BY WEIGHT, BASED ON THE WEIGHT OF POLYESTER RESIN, OF A POLYUNSATURATED COMPOUND OF THE FORMULA 